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Date:   Mon, 5 Jun 2023 14:47:16 -0500
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From:   Alex Elder <elder@linaro.org>
Subject: Re: [PATCH v13 01/24] dt-bindings: Add binding for gunyah hypervisor
To:     Elliot Berman <quic_eberman@quicinc.com>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc:     Murali Nalajala <quic_mnalajal@quicinc.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
        Carl van Schaik <quic_cvanscha@quicinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Will Deacon <will@kernel.org>, Andy Gross <agross@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, Rob Herring <robh@kernel.org>
References: <20230509204801.2824351-1-quic_eberman@quicinc.com>
 <20230509204801.2824351-2-quic_eberman@quicinc.com>
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On 5/9/23 3:47 PM, Elliot Berman wrote:
> When Linux is booted as a guest under the Gunyah hypervisor, the Gunyah
> Resource Manager applies a devicetree overlay describing the virtual
> platform configuration of the guest VM, such as the message queue
> capability IDs for communicating with the Resource Manager. This
> information is not otherwise discoverable by a VM: the Gunyah hypervisor
> core does not provide a direct interface to discover capability IDs nor
> a way to communicate with RM without having already known the
> corresponding message queue capability ID. Add the DT bindings that
> Gunyah adheres for the hypervisor node and message queues.
> 
> Reviewed-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>

Rob has reviewed this so I presume it's fine, but I wonder
why there's no "qcom," prefix on the compatible strings.

It also seems like there might be more bindings to define
for Gunyah.  See a few more comments below.

					-Alex

> ---
>   .../bindings/firmware/gunyah-hypervisor.yaml  | 82 +++++++++++++++++++
>   1 file changed, 82 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> 
> diff --git a/Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml b/Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> new file mode 100644
> index 000000000000..3fc0b043ac3c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> @@ -0,0 +1,82 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/firmware/gunyah-hypervisor.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Gunyah Hypervisor
> +
> +maintainers:
> +  - Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
> +  - Elliot Berman <quic_eberman@quicinc.com>
> +
> +description: |+
> +  Gunyah virtual machines use this information to determine the capability IDs
> +  of the message queues used to communicate with the Gunyah Resource Manager.
> +  See also: https://github.com/quic/gunyah-resource-manager/blob/develop/src/vm_creation/dto_construct.c

Looking at dto_create_msg_queue() at the above link, it seems
that Gunyah message queues and capabilities get represented
in DTS, but I don't see those things documented in bindings.
I might be misinterpreting that code, but if not, should
these other things be documented as well?

> +
> +properties:
> +  compatible:
> +    const: gunyah-hypervisor

Should this be qcom,gunyah-hypervisor?

> +
> +  "#address-cells":
> +    description: Number of cells needed to represent 64-bit capability IDs.
> +    const: 2
> +
> +  "#size-cells":
> +    description: must be 0, because capability IDs are not memory address
> +                  ranges and do not have a size.
> +    const: 0
> +
> +patternProperties:
> +  "^gunyah-resource-mgr(@.*)?":
> +    type: object
> +    description:
> +      Resource Manager node which is required to communicate to Resource
> +      Manager VM using Gunyah Message Queues.
> +
> +    properties:
> +      compatible:
> +        const: gunyah-resource-manager

Here too, should this be qcom,gunyah-resource-manager?

> +
> +      reg:
> +        items:
> +          - description: Gunyah capability ID of the TX message queue
> +          - description: Gunyah capability ID of the RX message queue
> +
> +      interrupts:
> +        items:
> +          - description: Interrupt for the TX message queue
> +          - description: Interrupt for the RX message queue
> +
> +    additionalProperties: false
> +
> +    required:
> +      - compatible
> +      - reg
> +      - interrupts
> +
> +additionalProperties: false
> +
> +required:
> +  - compatible
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +
> +    hypervisor {
> +        #address-cells = <2>;
> +        #size-cells = <0>;
> +        compatible = "gunyah-hypervisor";
> +
> +        gunyah-resource-mgr@0 {
> +            compatible = "gunyah-resource-manager";
> +            interrupts = <GIC_SPI 3 IRQ_TYPE_EDGE_RISING>, /* TX full IRQ */
> +                         <GIC_SPI 4 IRQ_TYPE_EDGE_RISING>; /* RX empty IRQ */
> +            reg = <0x00000000 0x00000000>, <0x00000000 0x00000001>;
> +                  /* TX, RX cap ids */
> +        };
> +    };